Frequency control device in a server, control method, and program

ABSTRACT

An in-server frequency control apparatus includes a preliminary grasp unit which preliminarily grasps a start of a service requiring low delay in a server and grasps termination of the service by a predetermined method, and an operating frequency change unit which changes an operating frequency of a CPU as a target to be controlled, which is a CPU allocated in advance to a receiver of the service in the server, at the time of the preliminarily grasped start of the service and at the time of the termination of the service. The operating frequency change unit makes the operating frequency of the target CPU higher than a predetermined value at the time of the start of the service and makes the operating frequency of the target CPU lower than the predetermined value at the time of the termination of the service.

TECHNICAL FIELD

The present invention relates to an in-server frequency controlapparatus, a control method, and a program.

BACKGROUND ART

As a technique for constructing a virtual machine, a hypervisorenvironment which is constructed using Linux (R) and KVM (kernel-basedvirtual machine) is well known. In such an environment, a host OS with abuilt-in KVM module operates as a hypervisor in a kernel space. In theenvironment, a virtual machine operates in a user space, and a guest OSoperates in the virtual machine. The host OS here refers to an OSinstalled on a physical server. The kernel space refers to a memoryregion different from the user space. The guest OS refers to an OSinstalled on the virtual machine.

Patent Literature 1 discloses a system in which a guest OS and a host OSare connected by virtio. In a virtual machine, for example, virtio-netis present as a virtio device for network communication. In this system,packet transfer processing is speeded up by decreasing the number oftimes memory copying related to virtio-net is done.

Patent Literature 2 discloses a system using SPP (Soft Patch Panel) asan extension of Intel DPDK (Intel Data Plane Development Kit) that is aset of high-speed packet processing libraries. Here, Intel is aregistered trademark. SPP performs, at high speed, packet copyingbetween a host OS and a guest OS and between guest OSes through zerocopy via a shared memory. In this system, setting of a route connectingvirtual machines is enabled by a GUI (Graphical User Interface)manipulation in SPP.

CITATION LIST Patent Literatures

-   Patent Literature 1: Japanese Patent Laid-Open No. 2015-197874-   Patent Literature 2: Japanese Patent Laid-Open No. 2018-032156

SUMMARY OF THE INVENTION Technical Problems

To implement a low-delay network end-to-end, it is necessary toimplement low delay in each section, such as an access section, atransmission section, a transfer section, a server section, or an APL(Application). Curbing of a delay in the server section is important toimplement a service high in real-time qualities. Additionally, thenumber of servers is increasing with a rapid increase in amount ofinformation in recent years, and power consumption is increasing. Forthis reason, it is also important to cut power consumption of servers.

As a conventional approach to achieving both high server processingperformance and power saving, there has been available an approach whichpredicts a processing load on a CPU and dynamically varies an operatingfrequency of the CPU. The approach is incorporated in the Linux kernelof recent years. Thus, the approach can be implemented by the techniquesdisclosed in Patent Literatures 1 and 2.

In the approach, a task scheduler manages, in the form of a queue, aprocess/thread task which is to use a CPU and predicts a load on eachCPU on the basis of the number of tasks accumulating in a queue anddynamically changes an operating frequency of the CPU. However, theapproach suffers a delay on the order of milliseconds. Since the taskscheduler does not manage, as a task, interruption processing, such aspacket processing, the task scheduler cannot predict a processing loadand does not change an operating frequency of a CPU. When a kernelreceives a packet while a CPU is operating at a low operating frequency,processing of the packet takes time, and a delay occurs. For thisreason, as an approach to curbing such a delay, an approach which causesa CPU to operate while keeping an operating frequency of the CPU highestis conceivable. However, the approach is assumed to increase powerconsumption of a CPU. In a case where a service conditional on low delayin a server section and power saving is provided, the two frequencysetting methods described above cannot meet the both conditions at thesame time.

Under the circumstances, the present invention has as its object tosolve the above-described problem and reduce power consumption of aserver while performing low-delay processing in the server.

Means for Solving the Problems

An in-server frequency control apparatus of the present inventionincludes: a preliminary grasp unit configured to preliminarily grasp astart of a service requiring low delay in a server and grasp terminationof the service by a predetermined method; and an operating frequencychange unit configured to change an operating frequency of a CPU as atarget to be controlled, the target CPU being allocated in advance to areceiver of the service in the server, at the time of the preliminarilygrasped start of the service and at the time of the termination of theservice. The operating frequency change unit is configured to make theoperating frequency of the target CPU higher than a predetermined valueat the time of the start of the service and also make the operatingfrequency of the target CPU lower than the predetermined value at thetime of the termination of the service.

Effects of the Invention

The present invention makes it possible to reduce power consumption of aserver while performing low-delay processing in the server.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram showing a receiver and transmitters in aconference call system according to an embodiment of the presentinvention.

FIG. 2 is a schematic configuration diagram of the conference callsystem according to the embodiment of the present invention.

FIG. 3 is a configuration diagram of an in-server frequency controlapparatus according to a first embodiment of the present invention.

FIG. 4 is a sequence chart showing the flow of a process of grasping asession state by the in-server frequency control apparatus according tothe first embodiment of the present invention.

FIG. 5 is a sequence chart showing the flow of a process after thein-server frequency control apparatus grasps session establishment.

FIG. 6 is a sequence chart showing the flow of a process after thein-server frequency control apparatus grasps session termination.

FIG. 7 is a configuration diagram of an in-server frequency controlapparatus according to a second embodiment of the present invention.

FIG. 8 is a flowchart showing the flow of a process of grasping aconference reservation status by the in-server frequency controlapparatus according to the second embodiment of the present invention.

FIG. 9 is a sequence chart showing the flow of a process after thein-server frequency control apparatus grasps a scheduled conferencestart.

FIG. 10 is a sequence chart showing the flow of a process after thein-server frequency control apparatus grasps conference termination.

FIG. 11 is a sequence chart showing a modification of the process ofgrasping a conference reservation status by the in-server frequencycontrol apparatus according to the second embodiment of the presentinvention.

FIG. 12 is a hardware configuration diagram showing an example of acomputer which implements functions of an in-server frequency controlapparatus according to an embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

An in-server frequency control apparatus of the present invention willbe described below in detail with reference to the drawings.

A description will be given on the assumption that an example of aservice (hereinafter simply referred to as a service) requiring lowdelay in a server is a conference call. First, a conference call systemto which the in-server frequency control apparatus is applied will bedescribed. A conference call system 1 shown in FIG. 1 includes an SIPserver 2 a and a media server 2 b. The SIP server 2 a performs sessioncontrol between telephone sets 4 and the media server 2 b using SIP(Session Initiation Protocol).

The media server 2 b implements a conference call 5 based on voicecommunication using, for example, RTP (Real-time Transport Protocol).The media server 2 b performs resampling, coding, and the like of mediadata, such as voice data, and generation of an RTP packet or the like,thereby implementing voice communication. The media server 2 b is areceiver of the conference call 5. The telephone set 4 is a transmitterof the conference call 5 and is used by a user which has a conferencecall. Note that the number of telephone sets 4 is not limited to threeshown in FIG. 1 .

As shown in FIG. 2 , the conference call system 1 includes an HW 20, anOS 21, and APLs 30, 30 a, 30 b, and 30 c in a user space in order toimplement the SIP server 2 a and the media server 2 b in FIG. 1 . The HW20 is hardware and includes a plurality of CPUs. By way of example, theHW 20 includes CPU0, CPU1, CPU2, and CPU3. The OS 21 is an operatingsystem and includes a kernel and software for packet processing. Thekernel is a function of a key portion of the operating system andmanages an execution state of a program on a per-process basis.

The APLs 30, 30 a, 30 b, and 30 c are application programs which operateon the OS 21. For example, CPU0 is allocated to the APL 30 a. The APL 30a is an application program which preliminarily manages a stream andfunctions as, for example, the SIP server 2 a. CPU0 makes datatransmission and reception communication with the APL 30 a via the OS21.

For example, CPU1 is allocated to the APL 30 b. The APL 30 b is anapplication program which executes a service and functions as, forexample, the media server 2 b. CPU1 makes data transmission andreception communication with the APL 30 b via the OS 21.

For example, CPU2 is allocated to the APL 30 c. The APL 30 c functionsas, for example, a reservation scheduler. The reservation schedulerperforms, for example, a process of reserving a conference call. CPU2makes data transmission and reception communication with the APL 30 cvia the OS 21. The APL 30 c functioning as the reservation scheduleraccepts a reservation of a conference call when a user reserves theconference call using an information terminal 6. The informationterminal 6 is composed of, for example, a general personal computer, atablet terminal, or a smartphone.

For example, CPU3 is allocated to the APL 30. The APL 30 functions as,for example, an in-server frequency control apparatus 10 in FIG. 3 .

First Embodiment

A conference call system including an in-server frequency controlapparatus 10 according to a first embodiment will be described withreference to FIG. 3 . Note that same components as those shown in FIG. 2are denoted by same reference characters and that a description thereofwill be omitted below.

The in-server frequency control apparatus 10 includes a preliminarygrasp unit 11 and an operating frequency change unit 12. The preliminarygrasp unit 11 preliminarily grasps a start of a service and graspstermination of the service by a predetermined method. The operatingfrequency change unit 12 changes an operating frequency of a CPU as atarget to be controlled, which is a CPU to which a service is allocatedin advance to a receiver of the service in a server, at the time of thepreliminarily grasped start of the service and at the time of thetermination of the service. The operating frequency change unit 12 makesthe operating frequency of the target CPU higher than a predeterminedvalue at the time of the start of the service and makes the operatingfrequency of the target CPU lower than the predetermined value at thetime of the termination of the service.

As shown in FIG. 3 , the preliminary grasp unit 11 includes, forexample, an event capture unit 23, an event processing unit 24, and asession state management unit 31. The operating frequency change unit 12includes, for example, a check command execution unit 25, a changecommand execution unit 26, a frequency check unit 32, and a frequencychange unit 33. Here, the OS 21 includes, as processing functions of akernel, a packet processing unit 22, the event capture unit 23, theevent processing unit 24, the check command execution unit 25, and thechange command execution unit 26. The session state management unit 31,the frequency check unit 32, and the frequency change unit 33 correspondto the APL 30 in FIG. 2 and operate on the OS 21. The OS 21 performs aprocess of changing an operating frequency of a CPU as a target to becontrolled. Assume that, for example, CPU3 is allocated to a kernelprocess of changing an operating frequency of a CPU. Note that any CPUcan be allocated to the kernel process of changing an operatingfrequency of a CPU and that CPU1 may be allocated.

Details of the units will be described below.

The packet processing unit 22 processes a packet related to SIPprocessing between CPU0 and the APL 30 a. For example, when the packetprocessing unit 22 receives an INVITE request packet which is a sessioncontrol start request from the telephone set 4, the packet processingunit 22 transfers the INVITE request packet to the SIP server 2 a. Thepacket processing unit 22 also transfers, for example, an INVITEresponse (200OK) packet, a session establishment acknowledgment (ACK)packet, and a session termination (BYE) packet.

The packet processing unit 22 also processes a packet related to mediaprocessing (RTP) between CPU1 and the APL 30 b. The packet processingunit 22 transfers a packet of media data, such as voice data, betweeneach telephone set (transmitter) 4 and the media server 2 b (receiver)after session establishment based on SIP.

The event capture unit 23 captures a phenomenon of occurrence of anevent which is registered in advance as an event of a Kernel process ofexecuting a service requiring low delay. When an event of a packetprocess occurs at a point registered in advance, the event capture unit23 notifies the event processing unit 24 of the occurrence of the event.

The present embodiment uses, for example, a kprobe (Kernel Probes), andsets, as a point, udp_rcv that is a UDP layer function and registers inadvance a reservation of a process to be performed on the occurrence ofan event of a packet process.

If a captured event is an event of a signal requesting sessionestablishment, the event processing unit 24 preliminarily grasps a startof a service and acquires a receiver and a session ID of the service asinformation on session establishment from the control signal. If thecaptured event is an event of a signal requesting session termination,the event processing unit 24 grasps termination of a service andacquires a receiver and a session ID of the service as information onsession termination from the control signal.

The event processing unit 24 is composed of, for example, eBPF (extendedBerkeley Packet Filter) bytecode. eBPF refers to a program which iscreated in a user space, is fed into the kernel, and operates inside thekernel. The event processing unit 24 executes a code which analyzes asignal and, if a result of the analysis indicates a signal of a processdetermined in advance, notifies a subsequent unit of informationnecessary for the subsequent unit. Specifically, if a signal of acaptured event indicates an “SIP processing signal” AND “ACK” when anotification signal from the event capture unit 23 arrives, the eventprocessing unit 24 notifies the session state management unit 31 of“ACK”, a “receiver”, and a “session ID”.

If a signal of a captured event indicates an “SIP processing signal” AND“200OK in response to BYE” when a notification signal from the eventcapture unit 23 arrives, the event processing unit 24 notifies thesession state management unit 31 of “200OK in response to BYE”, a“receiver”, and a “session ID”.

When a notification signal from the frequency check unit 32 arrives, thecheck command execution unit 25 checks a current operating frequency ofa target CPU designated by the notification signal and notifies thefrequency check unit 32 of the current operating frequency. The checkcommand execution unit 25 is composed of, for example, CPUfreq-info.

When a notification signal from the frequency change unit 33 arrives,the change command execution unit 26 changes an operating frequency of atarget CPU designated by the notification signal. The change commandexecution unit 26 is composed of, for example, CPUfreq-set.

The session state management unit 31 records a session ID of a servicein question in a session state management book 34 for a receiver of theservice and notifies the operating frequency change unit 12 of aninstruction to make an operating frequency of a CPU as a target to becontrolled higher if the session state management unit 31 acquiresinformation on session establishment.

The session state management unit 31 deletes a session ID of a servicein question from the session state management book 34 for a receiver ofthe service if the session state management unit 31 acquires informationon session termination. Additionally, if all session IDs are deletedfrom the session state management book 34 for the receiver of theservice, the session state management unit 31 notifies the operatingfrequency change unit 12 of an instruction to make the operatingfrequency of the target CPU lower.

The session state management book 34 holds a session ID. The heldsession ID refers to a session ID of a session which is established withthe media server 2 b.

The session state management unit 31 updates the session statemanagement book 34 for the media server 2 b when a notification signalfrom the event processing unit 24 arrives. Specifically, the sessionstate management unit 31 adds a session ID to the session statemanagement book 34 if an SIP processing signal indicates “ACK” when thenotification signal from the event processing unit 24 arrives. Thesession state management unit 31 deletes a session ID from the sessionstate management book 34 if the SIP processing signal indicates “200OKin response to BYE” when the notification signal from the eventprocessing unit 24 arrives.

Transmitters (the telephone sets 4) of a conference call and the sessionstate management book 34 have the following relationship. That is, whenthe conference call starts, the number of session IDs increases in thesession state management book 34. When a new participant joins theconference call during the conference call, the number of session IDsincreases in the session state management book 34. When one participantleaves the conference call during the conference call, the number ofsession IDs decreases in the session state management book 34. When theconference call terminates, there are no session ID entries left in thesession state management book 34.

If the session state management unit 31 refers to the updated sessionstate management book 34 and determines that the number of session IDshas increased, the session state management unit 31 notifies thefrequency check unit 32 of an instruction to make an operating frequencyof a CPU of a receiver of a conference call higher. Specifically, thesession state management unit 31 notifies the frequency check unit 32 ofinformation on the receiver and a high frequency flag.

If the session state management unit 31 refers to the updated sessionstate management book 34 and determines that there are no session IDentries left, the session state management unit 31 notifies thefrequency check unit 32 of an instruction to make the operatingfrequency of the CPU of the receiver of the conference call lower.Specifically, the session state management unit 31 notifies thefrequency check unit 32 of information on the receiver and a lowfrequency flag.

The information on the receiver here refers to identificationinformation on the media server 2 b. The high frequency flag meansmaking an operating frequency of a CPU as a target to be controlledhigher and is information paired with the low frequency flag. The highfrequency flag may be set to “H”, and the low frequency flag may be setto “L”. Alternatively, the high frequency flag may be set to “1”, andthe low frequency flag may be set to “0”.

If the frequency check unit 32 receives an instruction to change anoperating frequency of the target CPU from the preliminary grasp unit11, the frequency check unit 32 checks a current operating frequency ofthe CPU. The frequency check unit 32 notifies the check commandexecution unit 25 of a frequency check request. That is, the frequencycheck unit 32 requests the check command execution unit 25 to check thecurrent operating frequency of the CPU. When the frequency check unit 32receives the current operating frequency from the check commandexecution unit 25, the frequency check unit 32 notifies a subsequentunit of the current operating frequency together with informationnecessary for the subsequent unit.

The frequency check unit 32 identifies a CPU which is allocated to areceiver on the basis of a CPU allocation table 35 when a notificationsignal from the session state management unit 31 arrives. The CPUallocation table 35 is a correspondence table of CPU cores allocated torespective application programs. In the present embodiment, CPU1 isallocated to the media server 2 b that is a receiver. The frequencycheck unit 32 causes the check command execution unit 25 to execute acommand to check a current operating frequency for a CPU (CPU1) undercontrol. The frequency check unit 32 receives the current operatingfrequency of the CPU (CPU1) as a target to be controlled, from the checkcommand execution unit 25.

The frequency check unit 32 notifies the frequency change unit 33 ofinformation on the target CPU, the current operating frequency, and thehigh frequency flag if the number of session IDs increases, i.e., ifnotification of the high frequency flag is given.

The frequency check unit 32 notifies the frequency change unit 33 of theinformation on the target CPU, the current operating frequency, and thelow frequency flag if there are no session ID entries left, i.e., ifnotification of the low frequency flag is given.

The frequency change unit 33 changes an operating frequency of thetarget CPU in accordance with a result of comparing the currentoperating frequency of the CPU with a predetermined prescribed value.

The frequency change unit 33 makes the operating frequency of the targetCPU higher if the frequency change unit 33 receives an instruction tomake the operating frequency of the CPU higher from the preliminarygrasp unit 11, and the current operating frequency of the CPU is lessthan the prescribed value.

The frequency change unit 33 makes the operating frequency of the targetCPU lower if the frequency change unit 33 receives an instruction tomake the operating frequency of the CPU lower from the preliminary graspunit 11, and the current operating frequency of the CPU is more than theprescribed value.

The frequency change unit 33 performs the determination processing belowand checks whether it is necessary to change the operating frequency ofthe target CPU, on the basis of information, notification of which isgiven, when a notification signal from the frequency check unit 32arrives.

The frequency change unit 33 determines that it is necessary to make theoperating frequency of the target CPU higher in a case where a servicerequiring low delay is to be started. The case where a service requiringlow delay is to be started refers to a case where notification of thehigh frequency flag is given and the current operating frequency of theCPU is less than the prescribed value.

The frequency change unit 33 determines that it is necessary to make theoperating frequency of the target CPU lower in a case where a servicerequiring low delay has terminated. The case where a service requiringlow delay has terminated refers to a case where notification of the lowfrequency flag is given and the current operating frequency of the CPUis more than the prescribed value.

If no service requiring low delay is to be started, and no servicerequiring low delay has terminated, the frequency change unit 33determines that it is not necessary to change the operating frequency ofthe target CPU.

The frequency change unit 33 requests the change command execution unit26 to change the operating frequency of the target CPU if it isnecessary to change the operating frequency of the CPU.

[Control Method]

A control method for the in-server frequency control apparatus 10 willbe described with reference to FIGS. 4 to 6 (and appropriate referenceto FIG. 3 ). As shown in FIG. 4 , when the event capture unit 23 detectsan event of a Kernel process (step S101), the event capture unit 23returns to step S101 if the detected event is not a registered event (Noin step S102). On the other hand, if the detected event is a registeredevent (Yes in step S102), the event capture unit 23 notifies the eventprocessing unit 24 of detection of an event registered in advance (stepS103).

The event processing unit 24 receives an event notification signal ofthe event from the event capture unit 23 (step S104). The eventprocessing unit 24 analyzes whether a packet signal of the capturedevent is a signal which controls a stream (step S105). The eventprocessing unit 24, for example, determines that the packet signal is asignal which controls a stream (Yes in step S105) and that the controlsignal is a signal requesting session establishment (Yes in step S106).In this case, the event processing unit 24 acquires respective pieces ofinformation on session establishment, a session ID, and the receiverfrom the control signal (step S107). The event processing unit 24notifies the session state management unit 31 of the acquired pieces ofinformation (step S108). The session state management unit 31 receivessession establishment notification (step S109). Note that processes ofthe session state management unit 31 subsequent to step S109 will bedescribed with reference to a sequence chart in FIG. 5 .

As shown in FIG. 4 , the event processing unit 24, for example,determines that the control signal is not a signal requesting sessionestablishment (No in step S106) and is a signal requesting sessiontermination (Yes in step S110). In this case, the event processing unit24 acquires respective pieces of information on session termination, asession ID, and the receiver from the control signal (step S111). Theevent processing unit 24 notifies the session state management unit 31of the acquired pieces of information (step S112). The session statemanagement unit 31 receives session termination notification (stepS113). Note that processes of the session state management unit 31subsequent to step S113 will be described with reference to a sequencechart in FIG. 6 .

If the control signal is not a signal requesting session establishmentor session termination (No in step S110), as shown in FIG. 4 , the eventprocessing unit 24 returns to step S105. If the packet signal is not asignal which controls a stream in step S105 (No in step S105), the eventprocessing unit 24 returns to step S105.

The processes of the session state management unit 31 subsequent to stepS109 above will be described.

If the session state management unit 31 receives the sessionestablishment notification from the event processing unit 24 (stepS109), as shown in FIG. 5 , the session state management unit 31 addsthe session ID to the session state management book 34 for the receiver(step S201). The session state management unit 31 checks that the numberof session IDs has increased in the session state management book 34 forthe receiver (step S202). The session state management unit 31 acquiresthe information on the receiver and notifies the frequency check unit 32of the information on the receiver together with the high frequency flag(step S203).

The frequency check unit 32 acquires the information on the receiverwhen a notification signal from the session state management unit 31arrives. The frequency check unit 32 checks a CPU which is allocated tothe receiver in the CPU allocation table 35, on the basis of theinformation on the receiver (step S204). In this example, the frequencycheck unit 32 checks that the CPU allocated to the receiver is CPU′. Thefrequency check unit 32 notifies the check command execution unit 25 ofa frequency check request (step S205). The check command execution unit25 checks the current operating frequency of the target CPU and makes aresponse on the current operating frequency of the target CPU (stepS206). The frequency check unit 32 receives the current operatingfrequency of the target CPU and notifies the frequency change unit 33 ofan ID of the target CPU, the current operating frequency, and the highfrequency flag (step S207).

The frequency change unit 33, for example, receives the high frequencyflag and determines that the current operating frequency of the targetCPU is not less than the prescribed value (No in step S208). In thiscase, the frequency change unit 33 terminates the process. The frequencychange unit 33, for example, receives the high frequency flag anddetermines that the current operating frequency of the target CPU isless than the prescribed value (Yes in step S208). In this case, thefrequency change unit 33 notifies the change command execution unit 26of a request to make the operating frequency of the target CPU higher(step S209). The change command execution unit 26 makes the operatingfrequency of the target CPU higher (step S210). Thus, theabove-described processes make it possible to make the operatingfrequency of CPU1 allocated to the media server 2 b higher and provide alow-delay service when a session is established.

The processes of the session state management unit 31 subsequent to stepS113 above will be described.

If the session state management unit 31 receives the session terminationnotification from the event processing unit 24 (step S113), as shown inFIG. 6 , the session state management unit 31 deletes the session IDfrom the session state management book 34 for the receiver (step S301).The session state management unit 31 checks the updated session statemanagement book 34 for the receiver (step S302). The session statemanagement unit 31 makes an end of subsequent processing if the sessionstate management unit 31 determines that there is any session ID entryleft. The session state management unit 31 acquires the information onthe receiver and notifies the frequency check unit 32 of the informationon the receiver together with the low frequency flag (step S303) if thesession state management unit 31 determines that there are no session IDentries left.

The frequency check unit 32 acquires the information on the receiverwhen a notification signal from the session state management unit 31arrives. The frequency check unit 32 then checks a CPU which isallocated to the receiver in the CPU allocation table 35, on the basisof the information on the receiver (step S304). In this example, thefrequency check unit 32 checks that the CPU allocated to the receiver isCPU′. The frequency check unit 32 notifies the check command executionunit 25 of a frequency check request (step S305). The check commandexecution unit 25 checks the current operating frequency of the targetCPU and makes a response on the current operating frequency of thetarget CPU (step S306). The frequency check unit 32 receives the currentoperating frequency of the target CPU and notifies the frequency changeunit 33 of the ID of the target CPU, the current operating frequency,and the low frequency flag (step S307).

The frequency change unit 33, for example, receives the low frequencyflag and determines that the current operating frequency of the targetCPU is not more than the prescribed value (No in step S308). In thiscase, the frequency change unit 33 terminates the process. The frequencychange unit 33, for example, receives the low frequency flag anddetermines that the current operating frequency of the target CPU ismore than the prescribed value (Yes in step S308). In this case, thefrequency change unit 33 notifies the change command execution unit 26of a request to make the operating frequency of the target CPU lower(step S309). The change command execution unit 26 makes the operatingfrequency of the target CPU lower (step S310). Thus, the above-describedprocesses make it possible to make the operating frequency of CPU1allocated to the media server 2 b lower and reduce power consumptionwhen a session has terminated.

Second Embodiment

A conference call system including an in-server frequency controlapparatus 10B according to a second embodiment will be described withreference to FIG. 7 . Note that same components as those shown in FIG. 3are denoted by same reference characters and that a description thereofwill be omitted below. The in-server frequency control apparatus 10Bincludes a preliminary grasp unit 11B and an operating frequency changeunit 12. The preliminary grasp unit 11B includes, for example, areservation status management unit 36. The operating frequency changeunit 12 includes, for example, a frequency check unit 32, a checkcommand execution unit 25, a frequency change unit 33, and a changecommand execution unit 26. Here, an OS 21B includes, as processingfunctions of a kernel, a packet processing unit 22, the check commandexecution unit 25, and the change command execution unit 26. Thereservation status management unit 36 corresponds to the APL 30 in FIG.2 and operates on the OS 21B. Details of the units will be describedbelow.

The reservation status management unit 36 monitors a reservationscheduler and senses scheduled start information on a reserved serviceand termination information on the service. If the reservation statusmanagement unit 36 acquires scheduled start information on a servicebefore the service starts, the reservation status management unit 36preliminarily grasps a start of the service and records a transmitter ofthe service in a reservation status management book 37 for a receiver ofthe service. In this case, the reservation status management unit 36notifies the operating frequency change unit 12 of an instruction tomake an operating frequency of a CPU as a target to be controlledhigher. If the reservation status management unit 36 acquirestermination information on the service after the service terminates, thereservation status management unit 36 grasps the termination of theservice and deletes the transmitter of the service from the reservationstatus management book 37. If all transmitters are deleted from thereservation status management book 37, the reservation status managementunit 36 notifies the operating frequency change unit 12 of aninstruction to make the operating frequency of the target CPU lower.

In the present embodiment, the reservation status management unit 36monitors an APL 30 c functioning as a reservation scheduler atpredetermined time intervals (e.g., one-minute intervals). For example,if the reservation status management unit 36 accesses the APL 30 c atone-minute intervals, the reservation status management unit 36 cansense a scheduled start of a conference call one minute before a starttime of the conference call and sense termination of the conference callby one minute after a termination time of the conference call.

The reservation status management book 37 holds information on atransmitter of a conference call. The held information on thetransmitter refers to identification information on the transmitter, asession with a media server 2 b for which is to be established.Scheduled start information on a service is, for example, scheduledconference start information on a conference call. The scheduledconference start information is information on a receiver (the mediaserver 2 b), a transmitter (a telephone set 4), and a start time of theconference call. Termination information on a service is, for example,conference termination information on a conference call. The conferencetermination information is, for example, information on a receiver ofthe conference call, a transmitter, and a termination time of theconference call.

The reservation status management unit 36 updates the reservation statusmanagement book 37 for the media server 2 b when the reservation statusmanagement unit 36 acquires scheduled conference start information orconference termination information from the reservation scheduler.Specifically, when the reservation status management unit 36 acquiresscheduled conference start information from the reservation scheduler,the reservation status management unit 36 adds a transmitter to thereservation status management book 37 for the receiver a predeterminedtime (e.g., one minute) before a start time. If the reservation statusmanagement unit 36 acquires conference termination information from thereservation scheduler, the reservation status management unit 36 deletesa transmitter from the reservation status management book 37 for thereceiver a predetermined time (e.g., one minute) after a terminationtime.

Transmitters (the telephone sets 4) of a conference call and thereservation status management book 37 have the following relationship.That is, when the conference call starts, the number of transmittersincreases in the reservation status management book 37. When a newparticipant joins the conference call during the conference call, thenumber of transmitters increases in the reservation status managementbook 37. When one participant leaves the conference call during theconference call, the number of transmitters decreases in the reservationstatus management book 37. When the conference call terminates, thereare no transmitter entries left in the reservation status managementbook 37.

If the reservation status management unit 36 refers to the updatedreservation status management book 37 and determines that the number oftransmitters has increased, the reservation status management unit 36notifies the frequency check unit 32 of an instruction to make anoperating frequency of a CPU of the receiver of a conference callhigher. Specifically, the reservation status management unit 36 notifiesthe frequency check unit 32 of information on the receiver and a highfrequency flag.

If the reservation status management unit 36 refers to the updatedreservation status management book 37 and determines that there are notransmitter entries left, the reservation status management unit 36notifies the frequency check unit 32 of an instruction to make theoperating frequency of the CPU of the receiver of the conference callhigher. Specifically, the reservation status management unit 36 notifiesthe frequency check unit 32 of information on the receiver and a lowfrequency flag.

The information on the receiver here refers to identificationinformation on the media server 2 b.

[Control Method]

A control method for the in-server frequency control apparatus 10B willbe described with reference to FIGS. 8 to 10 (and appropriate referenceto FIG. 7 ). As shown in FIG. 8 , the reservation status management unit36 of the in-server frequency control apparatus 10B monitors the APL 30c as the reservation scheduler at, for example, one-minute intervals(step S401). The reservation status management unit 36 determineswhether there is any conference that is scheduled to start apredetermined time later (step S402). For example, the reservationstatus management unit 36 determines whether there is any conferencethat is scheduled to start within one minute from a current time. Ifthere is any conference scheduled to start (Yes in step S402), thereservation status management unit 36 acquires scheduled conferencestart information on the conference (step S403). That is, thereservation status management unit 36 acquires, as the scheduledconference start information, the receiver, a transmitter, and aconference call start time from the APL 30 c as the reservationscheduler. Note that processes of the reservation status management unit36 subsequent to step S403 will be described with reference to asequence chart in FIG. 9 .

If there is no conference scheduled to start (No in step S402), thereservation status management unit 36 determines whether there is anyconference terminated a predetermined time earlier (step S404). Forexample, the reservation status management unit 36 determines whetherthere is any conference call terminated within one minute from thecurrent time. If there is any terminated conference (Yes in step S404),the reservation status management unit 36 acquires conferencetermination information on the conference (step S405). That is, thereservation status management unit 36 acquires, as the conferencetermination information, the receiver, a transmitter, and a conferencecall termination time from the APL 30 c as the reservation scheduler.Processes of the reservation status management unit 36 subsequent tostep S405 will be described with reference to a sequence chart in FIG.10 . Note that, if there is no conference terminated the predeterminedtime earlier (No in step S404), as shown in FIG. 8 , the reservationstatus management unit 36 returns to step S401.

The processes of the reservation status management unit 36 subsequent tostep S403 above will be described.

As shown in FIG. 9 , if the reservation status management unit 36acquires scheduled conference start information from the scheduler (stepS403), the reservation status management unit 36 adds a transmitter tothe reservation status management book 37 for the receiver (step S501).The reservation status management unit 36 checks that the number oftransmitters has increased in the reservation status management book 37for the receiver (step S502). The reservation status management unit 36acquires information on the receiver and notifies the frequency checkunit 32 of the information on the receiver together with the highfrequency flag (step S503). Since processes in steps S204 to S210subsequent to step S503 are the same as steps S204 to S210 shown in FIG.5 , a description thereof will be omitted. Thus, the above-describedprocesses allow the in-server frequency control apparatus 10B to make anoperating frequency of CPU1 allocated to the media server 2 b higher andprovide a low-delay service when the in-server frequency controlapparatus 10B acquires scheduled conference start information from thescheduler.

The processes of the reservation status management unit 36 subsequent tostep S405 above will be described.

As shown in FIG. 10 , when the reservation status management unit 36acquires conference termination information from the scheduler (stepS405), the reservation status management unit 36 deletes a transmitterfrom the reservation status management book 37 for the receiver (stepS601). The reservation status management unit 36 checks the updatedreservation status management book 37 for the receiver (step S602). Thereservation status management unit 36 terminates subsequent processingif the reservation status management unit 36 determines that there isany transmitter entry left. The reservation status management unit 36acquires information on the receiver and notifies the frequency checkunit 32 of the information on the receiver together with the lowfrequency flag (step S603) if the reservation status management unit 36determines that there are no transmitter entries left. Since processesin steps S304 to S310 subsequent to step S603 are the same as in stepsS304 to S310 shown in FIG. 6 , a description thereof will be omitted.Thus, the above-described processes allow the in-server frequencycontrol apparatus 10B to make the operating frequency of CPU1 allocatedto the media server 2 b lower and reduce power consumption when aconference call terminates.

[Modification]

Although the in-server frequency control apparatus 10B according to thesecond embodiment is configured such that the reservation statusmanagement unit 36 monitors a reservation scheduler, the presentinvention is not limited to this. The reservation status management unit36 may be configured to receive notification of scheduled startinformation on a reserved service and termination information on theservice from a reservation scheduler each time a reservation update ismade.

In the case of the modification, as shown in FIG. 11 , the APL 30 c asthe reservation scheduler performs monitoring for an update toreservation information (step S701). The APL 30 c as the reservationscheduler determines whether there is any reservation informationupdated before a start of a conference (step S702). If there is anyreservation information updated before a start of a conference (Yes instep S702), the APL 30 c as the reservation scheduler notifies thereservation status management unit 36 of scheduled conference startinformation (step S703). Specifically, the APL 30 c as the reservationscheduler notifies the reservation status management unit 36 of areceiver, a transmitter, and a conference start time as the scheduledconference start information.

With the above-described notification, the reservation status managementunit 36 according to the modification acquires the scheduled conferencestart information (step S704). Since processes to be performed by thereservation status management unit 36 after step S704 are the same asthose in steps S501 to S503 shown in FIG. 9 , a description thereof willbe omitted. The processes in steps S204 to S210 subsequent to step S503are the same as in steps S204 to S210 shown in FIG. 5 , and adescription thereof will be omitted. Thus, the above-described processesallow the in-server frequency control apparatus 10B to make an operatingfrequency of CPU1 allocated to the media server 2 b higher and provide alow-delay service when the in-server frequency control apparatus 10Bacquires scheduled conference start information from the scheduler.

As shown in FIG. 11 , if there is no reservation information updatedbefore a start of a conference (No in step S702), the APL 30 c as thereservation scheduler determines whether there is any informationupdated due to conference termination (step S705). If there is noinformation updated due to conference termination (No in step S705), theAPL 30 c as the reservation scheduler returns to step S701. On the otherhand, if there is any information updated due to conference termination(Yes in step S705), the APL 30 c as the reservation scheduler notifiesthe reservation status management unit 36 of conference terminationinformation (step S706). Specifically, the APL 30 c as the reservationscheduler notifies the reservation status management unit 36 of areceiver, a transmitter, and a conference termination time as theconference termination information.

With the above-described notification, the reservation status managementunit 36 according to the modification acquires the conferencetermination information (step S707). Since processes to be performed bythe reservation status management unit 36 after step S707 are the sameas those in steps S601 to S603 shown in FIG. 10 , a description thereofwill be omitted. The processes in steps S304 to S310 subsequent to stepS603 are the same as in steps S304 to S310 shown in FIG. 6 , and adescription thereof will be omitted. Thus, the above-described processesallow the in-server frequency control apparatus 10B to make theoperating frequency of CPU1 allocated to the media server 2 b lower andreduce power consumption when a conference call terminates.

<Hardware Configuration>

The in-server frequency control apparatus 10 according to the presentembodiment is implemented by, for example, a computer 900 having aconfiguration as shown in FIG. 12 .

FIG. 12 is a hardware configuration diagram showing an example of thecomputer 900 that implements functions of the in-server frequencycontrol apparatus 10 according to the present embodiment. The computer900 has a CPU (Central Processing Unit) 901, a ROM (Read Only Memory)902, a RAM (Random Access Memory) 903, an HDD (Hard Disk Drive) 904, aninput-output I/F (Interface) 905, a communication I/F 906, and a mediaI/F 907.

The CPU 901 works on the basis of a program which is stored in the ROM902 or the HDD 904 and performs control by a control unit (thepreliminary grasp unit 11 and the operating frequency change unit 12shown in FIG. 3 ). The ROM 902 stores a boot program which is executedby the CPU 901 at the time of startup of the computer 900, a programrelated to hardware of the computer 900, and the like.

The CPU 901 controls an input device 910, such as a mouse or a keyboard,and an output device 911, such as a display or a printer, via theinput-output I/F 905. The CPU 901 acquires data from the input device910 and outputs generated data to the output device 911, via theinput-output I/F 905. Note that, as a processor, a GPU (GraphicsProcessing Unit) or the like may be used together with the CPU 901.

The HDD 904 stores a program to be executed by the CPU 901, data to beused by the program, and the like. The communication I/F 906 receivesdata from a different apparatus via a communication network 912 andoutputs the data to the CPU 901 or transmits data generated by the CPU901 to a different apparatus via the communication network 912.

The media I/F 907 reads a program or data stored in a recording medium913 and outputs the program or data to the CPU 901 via the RAM 903. TheCPU 901 loads a program related to a target process from the recordingmedium 913 into the RAM 903 via the media I/F 907 and executes theloaded program. The recording medium 913 is an optical recording medium,such as a DVD (Digital Versatile Disc) or a PD (Phase change rewritableDisk), a magneto-optical recording medium, such as an MO (MagnetoOptical disk), a magnetic recording medium, a conductor memory tapemedium, a semiconductor memory, or the like.

For example, if the computer 900 functions as the in-server frequencycontrol apparatus 10 according to the embodiment, the CPU 901 implementsthe functions of the in-server frequency control apparatus 10 byexecuting a program which is loaded into the RAM 903. Data in the RAM903 is stored in the HDD 904. The CPU 901 reads a program related to atarget process from the recording medium 913 and executes the program.Additionally, the CPU 901 may read the program related to the targetprocess from a different apparatus via the communication network 912.

When the computer 900 functions as the in-server frequency controlapparatus 10B according to the embodiment, the CPU 901 works similarlyon the basis of, for example, a program which is stored in the ROM 902or the HDD 904 and performs control by a control unit (the preliminarygrasp unit 11B and the operating frequency change unit 12 shown in FIG.7 ).

Advantageous Effects

As has been described above, the in-server frequency control apparatus10 includes the preliminary grasp unit 11 that preliminarily grasps astart of a service requiring low delay in a server and graspstermination of the service by a predetermined method and the operatingfrequency change unit 12 that changes an operating frequency of a CPU asa target to be controlled, which is a CPU allocated in advance to areceiver of the service in the server, at the time of the preliminarilygrasped start of the service and at the time of the termination of theservice, and the operating frequency change unit 12 makes the operatingfrequency of the target CPU higher than a predetermined value at thetime of the start of the service and makes the operating frequency ofthe target CPU lower than the predetermined value at the time of thetermination of the service.

With the above-described configuration, the in-server frequency controlapparatus 10 can grasp a time period requiring low delay in the serverand a time period not requiring low delay. Since the in-server frequencycontrol apparatus 10 sets an operating frequency of a CPU allocated to areceiver of a service requiring low delay higher at the time of a startof the service, the in-server frequency control apparatus 10 can providea service with low delay. Additionally, since the in-server frequencycontrol apparatus 10 sets the operating frequency of the CPU allocatedto the receiver of the service requiring low delay lower at the time oftermination of the service, the in-server frequency control apparatus 10can reduce power consumption. Thus, the in-server frequency controlapparatus 10 has an effect of achieving both low delay and power saving.

In the in-server frequency control apparatus 10, the preliminary graspunit 11 includes the event capture unit 23 that performs, as thepredetermined method, capturing a phenomenon of occurrence of an eventwhich is registered in advance as an event of a Kernel process ofexecuting a service requiring low delay, the event processing unit 24that preliminarily grasps a start of a service and acquires a receiverand a session ID of the service as information on session establishmentfrom a control signal requesting session establishment if a capturedevent is an event of the control signal and grasps termination of aservice and acquires a receiver and a session ID of the service asinformation on session termination from a control signal requestingsession termination if the captured event is an event of the controlsignal, and the session state management unit 31 that records a sessionID of a service in question in the session state management book 34 fora receiver of the service and notifies the operating frequency changeunit 12 of an instruction to make an operating frequency of a CPU undercontrol higher if the session state management unit 31 acquiresinformation on session establishment, and deletes a session ID of aservice in question from the session state management book 34 if thesession state management unit 31 acquires information on sessiontermination and notifies the operating frequency change unit 12 of aninstruction to make the operating frequency of the CPU as a target to becontrolled lower if all session IDS are deleted from the session statemanagement book 34.

With the above-described configuration, the in-server frequency controlapparatus 10 captures an event of a process of controlling a stream andanalyzes a session control signal at the time of occurrence of an event.If the in-server frequency control apparatus 10 grasps the fact that aservice requiring low delay is to start from a result of the analysis,the in-server frequency control apparatus 10 can preliminarily set anoperating frequency of a CPU allocated to a receiver of the servicehigher. If the in-server frequency control apparatus 10 grasps the factthat the service requiring low delay is to terminate, the in-serverfrequency control apparatus 10 can make the operating frequency of theCPU allocated to the receiver of the service lower.

In the in-server frequency control apparatus 10B, the preliminary graspunit 11B includes the reservation status management unit 36 thatperforms, as the predetermined method, monitoring a reservationscheduler which performs a process of reserving a service requiring lowdelay and sensing scheduled start information on a reserved service andtermination information on the service, and the reservation statusmanagement unit 36 preliminarily grasps a start of a service, records atransmitter of the service in the reservation status management book 37for a receiver of the service, and notifies the operating frequencychange unit 12 of an instruction to make an operating frequency of a CPUas a target to be controlled higher if the reservation status managementunit 36 acquires scheduled start information on the service before theservice starts, and grasps termination of a service and deletes atransmitter of the service from the reservation status management book37 if the reservation status management unit 36 acquires terminationinformation on the service after the service terminates and notifies theoperating frequency change unit 12 of an instruction to make theoperating frequency of the target CPU lower if all transmitters aredeleted from the reservation status management book 37.

With the above-described configuration, the in-server frequency controlapparatus 10B senses scheduled start information on a reserved serviceand termination information on the service by monitoring the reservationscheduler. If the in-server frequency control apparatus 10B grasps thefact that a service requiring low delay is to start, the in-serverfrequency control apparatus 10B can preliminarily set an operatingfrequency of a CPU allocated to a receiver of the service higher. If thein-server frequency control apparatus 10B grasps the fact that theservice requiring low delay is to terminate, the in-server frequencycontrol apparatus 10B can make the operating frequency of the CPUallocated to the receiver of the service lower.

In the in-server frequency control apparatus 10B, the preliminary graspunit 11B includes the reservation status management unit 36 thatperforms, as the predetermined method, receiving notification ofscheduled start information on a reserved service and terminationinformation on the service from the reservation scheduler that performsthe process of reserving a service requiring low delay each time areservation update is made, and the reservation status management unit36 preliminarily grasps a start of a service, records a transmitter ofthe service in the reservation status management book 37 for a receiverof the service, and notifies the operating frequency change unit 12 ofan instruction to make an operating frequency of a CPU as a target to becontrolled higher if the reservation status management unit 36 acquiresscheduled start information on the service before the service starts,and grasps termination of a service and deletes a transmitter of theservice from the reservation status management book 37 if thereservation status management unit 36 acquires termination informationon the service after the service terminates and notifies the operatingfrequency change unit 12 of an instruction to make the operatingfrequency of the target CPU lower if all transmitters are deleted fromthe reservation status management book 37.

With the above-described configuration, the in-server frequency controlapparatus 10B senses scheduled start information on a reserved serviceand termination information on the service by receiving notificationfrom the reservation scheduler each time a reservation update is made.If the in-server frequency control apparatus 10B grasps the fact that aservice requiring low delay is to start, the in-server frequency controlapparatus 10B can preliminarily set an operating frequency of a CPUallocated to a receiver of the service higher. If the in-serverfrequency control apparatus 10B grasps the fact that the servicerequiring low delay is to terminate, the in-server frequency controlapparatus 10B can make the operating frequency of the CPU allocated tothe receiver of the service lower.

In the in-server frequency control apparatus 10 or 10B, the operatingfrequency change unit 12 includes the frequency check unit 32 thatchecks a current operating frequency of a CPU as a target to becontrolled if the frequency check unit 32 receives an instruction tochange an operating frequency of the CPU from the preliminary grasp unit11 or 11B and the frequency change unit 33 that changes the operatingfrequency of the target CPU in accordance with a result of comparing thecurrent operating frequency of the CPU with a predetermined prescribedvalue, and the frequency change unit 33 makes the operating frequency ofthe target CPU higher if the frequency change unit 33 receives aninstruction to make the operating frequency of the CPU higher, and thecurrent operating frequency of the CPU is less than the prescribed valueand makes the operating frequency of the target CPU lower if thefrequency change unit 33 receives an instruction to make the operatingfrequency of the CPU lower, and the current operating frequency of theCPU is more than the prescribed value.

With the above-described configuration, the in-server frequency controlapparatus 10 or 10B checks whether it is necessary to change anoperating frequency of a CPU, on the basis of not only informationpreliminarily grasped by the preliminary grasp unit 11 or 11B but also acurrent operating frequency of the CPU. The in-server frequency controlapparatus 10 or 10B can make the operating frequency of the target CPUhigher if the in-server frequency control apparatus 10 or 10B grasps thefact that the current operating frequency of the CPU is low, and a timeperiod requiring low delay is to come. The in-server frequency controlapparatus 10 or 10B can make the operating frequency of the target CPUlower if the in-server frequency control apparatus 10 or 10B grasps thefact that the current operating frequency of the CPU is high, and it isa time period not requiring low delay.

Note that the present invention is not limited to the above-describedembodiments and that many modifications can be made within the technicalidea of the present invention by those skilled in the art. For example,an in-server frequency control apparatus can be applied to variousservices which need transferring of packets with low delay, besidesmedia processing of a conference call. An in-server frequency controlapparatus can be applied to various services which preliminarily managea real-time stream using, e.g., a session control signal. An in-serverfrequency control apparatus can be applied to various services whicheach have a time period requiring low-delay processing and a time periodnot requiring low-delay processing. An in-server frequency controlapparatus can provide a low-delay, low-power service by setting anoperating frequency of a CPU higher in a time period requiring low-delayprocessing and setting the operating frequency of the CPU lower in atime period not requiring low-delay processing.

REFERENCE SIGNS LIST

-   1 Conference call system-   2 a SIP server-   2 b Media server-   4 Telephone set-   5 Conference call-   6 Information terminal-   10, 10B In-server frequency control apparatus-   11 Preliminary grasp unit-   12 Operating frequency change unit-   20 HW-   21, 21B OS-   22 Packet processing unit-   23 Event capture unit-   24 Event processing unit-   25 Check command execution unit-   26 Change command execution unit-   30 a, 30 b, 30 c APL-   31 Session state management unit-   32 Frequency check unit-   33 Frequency change unit-   34 Session state management book-   35 CPU allocation table-   36 Reservation status management unit-   37 Reservation status management book

1-7. (canceled)
 8. An in-server frequency control apparatus, comprising:a preliminary grasp unit configured to preliminarily grasp a start of aservice requiring low delay in a server and grasp termination of theservice by a predetermined method; and an operating frequency changeunit configured to change an operating frequency of a CPU as a target tobe controlled, the target CPU being allocated in advance to a receiverof the service in the server, at the time of the preliminarily graspedstart of the service and at the time of the termination of the service,wherein the operating frequency change unit is configured to make theoperating frequency of the target CPU higher than a predetermined valueat the time of the start of the service and also make the operatingfrequency of the target CPU lower than the predetermined value at thetime of the termination of the service.
 9. The in-server frequencycontrol apparatus according to claim 8, wherein the preliminary graspunit comprises: an event capture unit configured to perform, as thepredetermined method, capturing a phenomenon of occurrence of an eventwhich is registered in advance as an event of a Kernel process ofexecuting the service requiring low delay; an event processing unitconfigured to, when the captured event is an event of a control signalrequesting a session establishment, preliminarily grasp the start of theservice and acquire a receiver and a session ID of the service asinformation on session establishment from the control signal and, whenthe captured event is an event of a control signal requesting a sessiontermination, grasp the termination of the service and acquire thereceiver and the session ID of the service as information on sessiontermination from the control signal; and a session state management unitconfigured to, when the session state management unit acquires theinformation on session establishment, record the session ID of theservice in a session state management book for the receiver of theservice and notify the operating frequency change unit of an instructionto make the operating frequency of the target CPU higher, and, when thesession state management unit acquires the information on sessiontermination, delete the session ID of the service from the session statemanagement book, and, further, when all of the session IDs are deletedfrom the session state management book, notify the operating frequencychange unit of an instruction to make the operating frequency of thetarget CPU lower.
 10. The in-server frequency control apparatusaccording to claim 8, wherein the preliminary grasp unit comprises afirst reservation status management unit configured to perform, as thepredetermined method, monitoring a reservation scheduler which performsa process of reserving the service requiring low delay and sensingscheduled start information on the reserved service and terminationinformation on the service, and wherein the first reservation statusmanagement unit is configured to, when the reservation status managementunit acquires the scheduled start information on a service before theservice starts, preliminarily grasp the start of the service, record atransmitter of the service in a reservation status management book for areceiver of the service, and notify the operating frequency change unitof an instruction to make the operating frequency of the target CPUhigher, and, when the reservation status management unit acquires thetermination information on the service after the service terminates,grasp the termination of the service and delete the transmitter of theservice from the reservation status management book, and, further, whenall of the transmitters are deleted from the reservation statusmanagement book, notify the operating frequency change unit of aninstruction to make the operating frequency of the target CPU lower. 11.The in-server frequency control apparatus according to claim 8, whereinthe preliminary grasp unit comprises a second reservation statusmanagement unit configured to perform, as the predetermined method,receiving notification of scheduled start information on the reservedservice and termination information on the service from a reservationscheduler which performs a process of reserving the service requiringlow delay each time a reservation update is made, and wherein thereservation status management unit is configured to, when thereservation status management unit acquires the scheduled startinformation on the service before the service starts, preliminarilygrasp the start of the service, record a transmitter of the service in areservation status management book for the receiver of the service, andnotify the operating frequency change unit of an instruction to make theoperating frequency of the CPU under control higher, and, when thereservation status management unit acquires the termination informationon the service after the service terminates, grasp the termination ofthe service and delete the transmitter of the service from thereservation status management book, and, further, when all of thetransmitters are deleted from the reservation status management book,notify the operating frequency change unit of an instruction to make theoperating frequency of the target CPU lower.
 12. The in-server frequencycontrol apparatus according to claim 9, wherein the operating frequencychange unit comprises: a frequency check unit configured to, when thefrequency check unit receives an instruction to change the operatingfrequency of the target CPU from the preliminary grasp unit, check acurrent operating frequency of the target CPU; and a frequency changeunit configured to change the operating frequency of the target CPU inaccordance with a result of comparing the current operating frequency ofthe CPU with a predetermined prescribed value, wherein the frequencychange unit is configured to, when the frequency change unit receives aninstruction to make the operating frequency of the CPU higher and alsowhen the current operating frequency of the CPU is less than theprescribed value, make the operating frequency of the target CPU higher,and, when the frequency change unit receives an instruction to make theoperating frequency of the CPU lower and also when the current operatingfrequency of the CPU is more than the prescribed value, make theoperating frequency of the target CPU lower.
 13. The in-server frequencycontrol apparatus according to claim 10, wherein the operating frequencychange unit comprises: a frequency check unit configured to, when thefrequency check unit receives an instruction to change the operatingfrequency of the target CPU from the preliminary grasp unit, check acurrent operating frequency of the target CPU; and a frequency changeunit configured to change the operating frequency of the target CPU inaccordance with a result of comparing the current operating frequency ofthe CPU with a predetermined prescribed value, wherein the frequencychange unit is configured to, when the frequency change unit receives aninstruction to make the operating frequency of the CPU higher and alsowhen the current operating frequency of the CPU is less than theprescribed value, make the operating frequency of the target CPU higher,and, when the frequency change unit receives an instruction to make theoperating frequency of the CPU lower and also when the current operatingfrequency of the CPU is more than the prescribed value, make theoperating frequency of the target CPU lower.
 14. The in-server frequencycontrol apparatus according to claim 11, wherein the operating frequencychange unit comprises: a frequency check unit configured to, when thefrequency check unit receives an instruction to change the operatingfrequency of the target CPU from the preliminary grasp unit, check acurrent operating frequency of the target CPU; and a frequency changeunit configured to change the operating frequency of the target CPU inaccordance with a result of comparing the current operating frequency ofthe CPU with a predetermined prescribed value, wherein the frequencychange unit is configured to, when the frequency change unit receives aninstruction to make the operating frequency of the CPU higher and alsowhen the current operating frequency of the CPU is less than theprescribed value, make the operating frequency of the target CPU higher,and, when the frequency change unit receives an instruction to make theoperating frequency of the CPU lower and also when the current operatingfrequency of the CPU is more than the prescribed value, make theoperating frequency of the target CPU lower.
 15. A control methodperformed by an in-server frequency control apparatus arranged in aserver, the control method, comprising: a step of preliminarily graspinga start of a service requiring low delay in the server and also graspingtermination of the service by a predetermined method; and a step ofchanging an operating frequency of a CPU as a target to be controlled,the target CPU being allocated in advance to a receiver of the servicein the server, at the time of the preliminarily grasped start of theservice and at the time of the termination of the service, wherein, inthe step of changing the operating frequency, at the time of the startof the service, the operating frequency of the target CPU is made higherthan a predetermined value, and, at the time of the termination of theservice, the operating frequency of the target CPU is made lower thanthe predetermined value.
 16. A program product for causing a computer asan in-server frequency control apparatus arranged in a server toexecute: a preliminary grasp procedure for preliminarily grasping astart of a service requiring low delay in a server and graspingtermination of the service by a predetermined method; and an operatingfrequency change procedure for changing an operating frequency of a CPUas a target to be controlled, the target CPU being allocated in advanceto a receiver of the service in the server, at the time of thepreliminarily grasped start of the service and at the time of thetermination of the service, wherein, in the operating frequency changeprocedure, at the time of the start of the service, the operatingfrequency of the target CPU is made higher than a predetermined value,and, at the time of the termination of the service, the operatingfrequency of the target CPU is made lower than the predetermined value.